This invention relates to blood pressure measurement in general and in particular to automatic blood pressure monitoring systems. Still more particularly, this invention relates to methods and apparatus for accurately monitoring blood pressure during stress testing or other physical activity as well as when quiescent.
One of the major medical problems facing the public today is associated with the lack of control of abnormal blood pressure. Indeed, hypertension is a leading cause of disease and death in the United States and it has been estimated that over fifteen percent of the United States population has hypertension at present, controlled by intermittent oral therapy or emergency intravenous medication.
For control of abnormal blood pressure, accurate and dependable measurement of blood pressure is necessary both to determine the presence of a problem and for monitoring the pressure to assure alleviation or control of such problem. In particular, it is highly useful for the medical practitioner to determine a patient's blood pressure during physical activity such as during a diagnostic stress test; however, such testing generally results in severe and frequent arm motions which generate a large number of false signals known as motion artifacts.
As a result of the problems generated by these motion artifacts, numerous attempts have been made to provide an apparatus for measuring systolic and diastolic blood pressure during such testing in which artifact information may be substantially eliminated from Korotkov sound signals which are employed to determine blood pressure. One example of such a system is disclosed in U.S. Pat. No. 4,408,614, issued to Charles S. Weaver et al. Weaver et al provides an automatic computer-implemented technique for identifying and eliminating false outputs from a Korotkov sound detector included in a blood pressure measuring system or the like which is adapted for use during stress testing. The Weaver et al patent discloses a method by which a group of points of data may be operated on to delete suspected artifact points and enhance the accuracy of blood pressure measurement.
A second example of blood pressure measurement is disclosed in U.S. Pat. No. 4,425,920, issued to Bourland et al. Bourland et al discloses an apparatus and method for the measurement and control of blood pressure in which blood pressure is indirectly monitored without the use of a pressure transducer by sensing the pulse transit time to different sites within an artery. The transit time is inversely related to the blood pressure and pulses which are developed therefrom are utilized to form arterial pulse waves, the comparison between which provides an indication of measured blood pressure.
While known systems do generally provide some degree of enhanced accuracy due to partial elimination of motion artifact, it is generally accepted that an improved blood pressure monitoring system which may be utilized during diagnostic stress testing would be highly desired.